Cleaning agents for the outer surfaces of means of transport

ABSTRACT

The invention relates to the use of a composition for cleaning the outside of a means of transport. The composition contains component a) at least one tertiary amino oxide of formula R 1  R 2  R 3  NO, whereby R 1  represents an alkylamidoalkyl, alkenylamidoalkyl, alkoxypropylamidoalkyl or alkenylamidoalkyl group having between 8–18 carbon atoms, R 2  and R 3  represent, independently from each other, low molecular alkyl radicals or hydroxyethyl radicals or hydroxypropyl radicals, and component b) at least one alkali metal salt of polyasparaginic acid having a molecular weight of between 5,000 g/mol–50,000 g/mol, or a polyglutaminic acid having a molecular weight of between 5,000 g/mol–50,000 g/mol, or a mixture of both substances, whereby the weight ratio of the components a:b is between 10:1 and 3000:1. The cleaner of the present invention effectively removes dirt and comprises environmentally friendly corrosion inhibitors.

The present invention relates to cleaning compositions for removingsevere contamination from exterior surfaces of means of transport,comprising amine oxides and polypeptides.

On the exterior surfaces of means of transport, such as automobiles,trucks, trains, streetcars, and aircraft in particular, for example,severe, difficult-to-remove soiling is a regular occurrence.Particularly on the outer skin of aircraft, such soiling is intolerable.

Aircraft exterior cleaners do not serve exclusively for cleaning dirtyaircraft; rather, they are also essential for the economic operation ofaircraft. In the course of flight operation, aluminum surfaces onaircraft become permanently contaminated by airfuel, carbon from thewaste combustion gases, and lubricant. As a result of the soiling thesurface roughness increases, and so the airflow necessary for liftbecomes slightly more turbulent. As a result, an increased propulsionforce and hence also more fuel is needed in order to hold the aircraftat the desired speed of travel. Contamination may additionally causecorrosion of the aluminum components, which can lead to significantimpairment of flying safety.

Aircraft exterior cleaners are required to satisfy a large number ofrequirements. In accordance with the SAE specification AMS (AerospaceMaterial Standards) 1526 (cleaner for aircraft exterior surfaces,water-miscible, pressure-spraying type) corrosiveness, hydrogenembrittlement, materials compatibility, and the stability of thecleaning composition are investigated.

In the state of the art there are known aircraft exterior cleaners whichare aqueous solutions of surfactants, organic solvents, and inorganicsubstances. The inorganic ingredients promote the abrasion of the dirtparticles. However, these water-insoluble constituents often give riseto a matt film on the aircraft surface, unless the cleaner is rinsed offfully with clean water afterward. In the disposal of the cleaners, theorganic solvents are very harmful to aquatic organisms. In addition theycause unpleasant odors and, as a result of their low vapor pressure,they increase the risk of ignition.

In the state of the art, aircraft cleaning compositions have generallybeen formulated with poorly degradable and environmentally hazardouscorrosion inhibitors, such as sodium nitrate, sodium nitrite orthiourea.

U.S. Pat. No. 3,458,300 discloses a cleaner which comprises aluminumoxide particles intended to remove the dirt from aircraft surfaces byabrasion. Surfactants with an antistatic action prevent the dirtparticles resettling on the outer skin.

U.S. Pat. No. 3,491,027 discloses a cleaning solution which is employedon aircraft which operate predominantly in the vicinity of the sea. Thecomposition is suitable for removing salt deposits from aircraftsurfaces.

U.S. Pat. No. 3,948,819 discloses the synergistic effect obtainedthrough the choice of two nonionic surfactants as dirt dissolvers. Amethod is described for assessing the cleaning effect.

U.S. Pat. No. 5,496,413 discloses the combination of cleaning and waxingcomponents in a single cleaner.

U.S. Pat. No. 5,516,459 discloses the use of alkylamine oxides inthickened aircraft exterior cleaners; however, the cleaner has a pHwhich is well within the alkaline range, and requires environmentallyharmful alkali metal nitrites for inhibiting corrosion.

U.S. Pat. No. 5,880,078 discloses how the desired dirt dissolutioncharacteristics can be obtained by means of a combination of ethoxylatedfatty alcohols having different HLB values.

From the state of the art it is clear that the development of aircraftexterior cleaners has to date concentrated almost exclusively onimproving the cleaning effect. Only little effort has so far beenexpended on formulating aircraft exterior cleaners simultaneously withmore environmentally compatible corrosion inhibitors.

The object of the invention was therefore to develop an aircraftexterior cleaner which not only effectively removes dirt but alsocomprises environmentally friendly corrosion inhibitors. The cleanerought also to be free from solvents and other substances which, owing totheir low vapor pressure, may cause unpleasant odors, are readilyignitable, and, furthermore, may be hazardous to health. The cleanershould be suitable not only for aircraft but also for other means oftransport.

Surprisingly it has now been found that cleaning compositions based ontertiary amine oxides and polypeptides as corrosion inhibitors have aparticularly good activity.

The invention accordingly provides for the use of a composition for theexterior cleaning of means of transport, comprising

a) at least one tertiary amine oxide of the formula R₁R₂R₃NO, where

-   -   R₁ is an alkyl, alkenyl, alkoxypropyl or alkenylamidoalkyl group        having 8 to 18 carbon atoms,    -   R₂ and R₃ independently of one another are low molecular mass        alkyl radicals or hydroxyethyl or hydroxypropyl radicals,

b) at least one alkali metal salt of polyaspartic acid, having amolecular weight of from 5000 g/mol to 50 000 g/mol, or of polyglutamicacid, having a molecular weight of from 5000 g/mol to 50 000 g/mol, or amixture of both substances, the weight ratio of the constituents a):b),being between 10:1 and 3000:1.

Weight percentages below are in each case based on the weight of thecomposition. In one preferred embodiment the composition contains 10 to30% by weight of constituent a), 0.01 to 1% by weight of constituent b),and water to 100% by weight. The preferred weight ratio betweenconstituents a) and b) is between 15:1 and 2500:1.

The invention preferably provides for the use of the composition of theinvention as an exterior cleaning composition for aircraft.

The invention further provides a method for the exterior cleaning ofmeans of transport, in particular of aircraft, by applying thecomposition of the invention to the outer skin of the means of transportthat is to be cleaned.

Constituent a) of the composition of the invention makes up preferably15 to 25% by weight of the total weight. R₁ is preferably an alkyl,alkenyl, alkoxypropyl or alkenylamidoalkyl group having 10 to 16 carbonatoms. R₂ and R₃ are preferably alkyl radicals having 1 to 6, inparticular 1 to 4, carbon atoms or else can be hydroxyethyl orhydroxypropyl radicals. Examples of constituent a) that may be mentionedinclude the following: cocoalkyldimethylamine oxide,stearyldimethylamine oxide, lauryldimethylamine oxide, andC₁₄-alkyldimethylamine oxide. Component a) can also be a mixture of saidamine oxides.

Constituent b) is an alkali metal salt of polyaspartic acid or ofpolyglutamic acid, having a molecular weight of preferably from 7000g/mol to 20 000 g/mol, or a mixture of both substances. These arereadily degradable, nontoxic, and water-soluble biopolymers, in thiscase specifically polypeptides. To date these compounds have been usedprimarily as dispersants in cooling water and for removing limedeposits. It has become apparent that these substances are likewiseoutstandingly suitable as corrosion inhibitors for use in aircraftexterior cleaners. In addition, defoamers, dyes, complexing agents, andantioxidants may be present in the cleaners.

The pH of aircraft exterior cleaners ought generally to be from 6.5 to11, preferably 9 to 10. If the composition of the invention does nothave such a pH, the pH can be adjusted by means of suitable pHregulators. Basic compounds suitable for this purpose are those from thegroup of the alkali metal hydroxides, such as NaOH and KOH.

The composition of the invention is prepared by mixing the individualconstituents in any order, which can be done, for example, in a vesselequipped with stirrer.

The resulting formulations exhibit an outstanding dirt dissolutionpower. Practical tests on motor vehicles have shown that they can beused to remove easily even stubborn insect contamination on windshields.The composition does not leave any streaks, contains no organicsolvents, and contains only environmentally friendly and readilydegradable corrosion inhibitors.

Slight soiling can be removed without problems with the cleaner diluted1:15 with water. In the case of stubborn soiling a dilution of 1:5 isrecommended.

The invention is now illustrated by examples.

EXAMPLES

The cleaning effect is assessed by means of dirt dissolution tests. Forthis purpose a 2024-T3 aluminum panel measuring 5×2 cm with a thicknessof 1 mm is used. Before the beginning of the test, the aluminum panel isetched first with a dilute sodium hydroxide solution and then with adilute nitric acid solution. This roughens the surface, so thatparticles of dirt are better able to settle on the panel. The panel isprovided alternately with different forms of contamination. Theseinclude bearing grease, vaseline, and synthetic aircraft soiling.

100 g of this synthetic aircraft soiling are composed of 1 g of lanolin,20 g of activated carbon, 10 g of talc, 15 g of lubricating oil, and 54g of kerosene. The components are intimately mixed with one another andapplied in a thin film to the aluminum panel. The dirt is subsequentlybaked into the aluminum panel at 100° C. in a drying oven for 12 hours.

In order to assess the dirt dissolution power, the aluminum paneltreated with bearing grease, vaseline or synthetic aircraft soiling isimmersed in a solution of 100 ml of cleaning composition. The solutionis in a glass beaker in which a magnetic stirrer rotates at 500revolutions per minute. At regular intervals an assessment is made ofthe dirt components which have detached.

Example 1

An inventive aircraft cleaning composition is prepared by mixing thefollowing components (concentrate):

15.00% by weight C₁₂/C₁₄-alkyldimethylamine oxide  0.20% by weightalkali metal polyaspartate with 15 000 g/mol  0.45% by weight sodiumhydroxide 84.35% by weight water.

The dirt dissolution power of this cleaning composition is investigatedon the basis of the method described above. Within just a few minutes,both the concentrate and the 1:1 and 1:2 dilutions with water detach thebearing grease, vaseline, and synthetic aircraft soiling contaminantscompletely from the aluminum plates.

Further investigations on the aircraft cleaning composition described inexample 1 reveal that all of the other requirements of the SAEspecification AMS 1526 are met. The composition causes no corrosion toaluminum, magnesium, and steel alloys and adversely affects neitheracrylic glass nor painted and unpainted aircraft surfaces.

Example 2

An inventive aircraft cleaning composition is prepared by mixing thefollowing components (concentrate):

25.00% by weight lauryldimethylamine oxide  0.20% by weight alkali metalpolyglutamate with 35 000 g/mol  0.40% by weight potassium hydroxide 74.4% by weight water.

This cleaning composition likewise detaches all contaminants and meetsthe requirements of SAE specification AMS 1526.

Example 3

An inventive aircraft cleaning composition is prepared by mixing thefollowing components (concentrate):

20.00% by weight cocoalkyldimethylamine oxide  0.20% by weight alkalimetal polyaspartate with 10 000 g/mol  0.35% by weight sodium hydroxide79.45% by weight water.

This cleaning composition likewise detaches all contaminants and meetsthe requirements of SAE specification AMS 1526.

1. A method for cleaning an exterior surface of a selected from thegroup consisting of automobile, a truck, a train, a streetcar, and anaircraft means of transport composition, said method comprisingcontacting said means of transport with a composition comprising: a) atleast one tertiary amine oxide of the formula R₁R₂R₃NO, where R₁ is analkyl, alkenyl, alkoxypropyl or alkenylamidoalkyl group having 8 to 18carbon atoms, R₂ and R₃ independently of one another are of 1 to 6carbon atoms alkyl radicals of 1 to 6 crabon atoms, or hydroxyethylhydroxyethyl radicals, and b) at least one alkali metal salt of an acidselected from the group consisting of a polyaspartic acid, apolyglutamic acid, or a mixture thereof, said acid having a molecularweight of from 5000 g/mol to 50 000 g/mol, wherein a weight ratio of theconstituents a):b) is between 10:1 and 3000:1.
 2. The method of claim 1,wherein R₁ is selected from the group consisting of an alkyl, alkenyl,alkoxypropyl, alkenylamido, and mixtures thereof wherein R₁ has 10 to 16carbon atoms.
 3. The method of claim 1, wherein the molecular weight ofb) is from 7000 to 20 000 g/mol.
 4. The method of claim 1, wherein thecomposition further comprises a compound selected from the groupconsisting of defoamers, dyes, complexing agents, antioxidants andmixtures thereof.
 5. The method of claim 1 wherein the means oftransport is an aircraft.